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BeforeFinalReturn.java
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BeforeFinalReturn.java
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/*
* This file is part of Mixin, licensed under the MIT License (MIT).
*
* Copyright (c) SpongePowered <https://www.spongepowered.org>
* Copyright (c) contributors
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package org.spongepowered.asm.mixin.injection.points;
import java.util.Collection;
import java.util.ListIterator;
import org.spongepowered.asm.lib.Opcodes;
import org.spongepowered.asm.lib.Type;
import org.spongepowered.asm.lib.tree.AbstractInsnNode;
import org.spongepowered.asm.lib.tree.InsnList;
import org.spongepowered.asm.lib.tree.InsnNode;
import org.spongepowered.asm.mixin.injection.InjectionPoint;
import org.spongepowered.asm.mixin.injection.InjectionPoint.AtCode;
import org.spongepowered.asm.mixin.injection.struct.InjectionPointData;
import org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException;
import org.spongepowered.asm.mixin.refmap.IMixinContext;
/**
* <p>This injection point searches for the last RETURN opcode in the target
* method and returns it. Note that the last RETURN opcode may not correspond to
* the notional "bottom" of a method in the original Java source, since
* conditional expressions can cause the bytecode emitted to differ
* significantly in order from the original Java.</p>
*
* <p>Example:</p>
* <blockquote><pre>
* @At(value = "TAIL")</pre>
* </blockquote>
* <p>Note that if <em>value</em> is the only parameter specified, it can be
* omitted:</p>
* <blockquote><pre>
* @At("TAIL")</pre>
* </blockquote>
*/
@AtCode("TAIL")
public class BeforeFinalReturn extends InjectionPoint {
private final IMixinContext context;
public BeforeFinalReturn(InjectionPointData data) {
super(data);
this.context = data.getContext();
}
@Override
public boolean checkPriority(int targetPriority, int ownerPriority) {
return true;
}
@Override
public boolean find(String desc, InsnList insns, Collection<AbstractInsnNode> nodes) {
AbstractInsnNode ret = null;
// RETURN opcode varies based on return type, thus we calculate what opcode we're actually looking for by inspecting the target method
int returnOpcode = Type.getReturnType(desc).getOpcode(Opcodes.IRETURN);
ListIterator<AbstractInsnNode> iter = insns.iterator();
while (iter.hasNext()) {
AbstractInsnNode insn = iter.next();
if (insn instanceof InsnNode && insn.getOpcode() == returnOpcode) {
ret = insn;
}
}
// WAT?
if (ret == null) {
throw new InvalidInjectionException(this.context, "TAIL could not locate a valid RETURN in the target method!");
}
nodes.add(ret);
return true;
}
}